Struts supports two types of validation
1)"pro grammatical validations" ,performed using
validate()method in form bean.
public ActionErrors validate(ActionMapping mapping,
			HttpServletRequest request) {
}
validate method return type is ActionErrors ,it holds set of
ActionError objects.


2)"declarative validations" ,handled by struts frame work only.
Struts provides a XML file validator-rules.xml which
contains standard validation methods

so this fie is configured into our application like this in
struts-config.xml file using <plug-in >tag.
we are having the responsibility inform to framework which
validations only u are using in Ur applications.that
particular keys can be defined in validation.xml file.
this file also configured in struts-config.xml
<plug-in
className="org.apache.struts.validator.ValidatorPlugIn">
		<set-property property="pathnames"
			value="/org/apache/struts/validator/validator-rules.xml,
               /WEB-INF/validation.xml" />
	</plug-in>